I have a 2002 Elantra that has been in shop 3xs for same thing. The car says it is missfiring on 1 and I have changed wires, coil pack and spark plugs with no success. Please help!!!
Could be many things. Does it do it standing still or only at higher speeds?
Check compression in all cylinders. You may have a bad valve or worn rings.
What kind of “shop” have you taken it to?